The methylamines, mono-, di- and trimethylamine, are commodities in the chemical industry, widely used as starting materials in the preparation of other chemicals.
The methylamines can be prepared by several methods. The most common of these is the continuous catalytic reaction of methanol or dimethyl ether and ammonia, using an aluminosilicate as a dehydration catalyst.
Under typical commercial operating conditions (400.degree. C., 300 psig pressure and a nitrogen/carbon ratio of 1), that reaction produces an equilibrium mixture of about 15%, by weight of monomethylamine (MMA), about 23% of dimethylamine (DMA) and about 62% of trimethylamine (TMA). The composition of the mixture is a constant problem in that individual market demands for MMA, DMA and TMA vary greatly from one period to the next and are generally out of phase with what is produced. For example, the call for TMA is generally sluggish and production often far exceeds demand. This is ordinarily taken care of by recycling excess TMA product to the reactor to produce more MMA and DMA, each of which is more easily absorbed by the marketplace.
It has now been found that this problem can be more efficiently resolved by using as the catalyst for the methanol-ammonia reaction an amorphous aluminosilicate which contains about 0.1-6%, by weight, of sodium, potassium, lithium, barium or strontium atoms as a result of treating an aluminosilicate with a corresponding metal hydroxide. By varying the treatment conditions, as will be explained, one can direct the reaction to produce less than an equilibrium amount of TMA, thus dictating that the process produce more MMA and DMA.